astronomy

noun

as·​tron·​o·​my ə-ˈsträ-nə-mē 

plural astronomies

: the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties

Did you know?

The Difference Between Astronomy and Astrology

Some may find it easy to confuse astronomy and astrology. At one time, these two words actually were synonymous (that is, astronomy once meant what astrology means today), but they have since moved apart from each other. In current use, astronomy is concerned with “the study of objects and matter outside the earth's atmosphere,” while astrology is the purported divination of how stars and planets influence our lives. Put bluntly, astronomy is a science, and astrology is not.

Examples of astronomy in a Sentence

Recent Examples on the Web

Eric Berger is the senior space editor at Ars Technica, covering everything from astronomy to private space to NASA policy, and author of two books: Liftoff, about the rise of SpaceX; and Reentry, on the development of the Falcon 9 rocket and Dragon. —Ars Technica, 7 Feb. 2025

Here’s what to know about the upcoming astronomy events: How to see 6 planets and crescent moon Once the sun goes down on Monday, Feb. 3, six planets and the moon will line up across the California night sky. —Hannah Poukish, Sacramento Bee, 31 Jan. 2025

With expert astronomy guidance, sea-aged wine, and learning about Indigenous culture, Hurtigruten offers a fresh perspective on aurora viewing in Arctic Norway. —Ryan Craggs, Travel + Leisure, 31 Jan. 2025

Mitton said the observatory is a memorial that continues Rubin’s mission to include not just many people in astronomy, but more of those who haven’t historically gotten a chance to make their mark. —Lisa Song, ProPublica, 30 Jan. 2025

Word History

Etymology

Middle English astronomie "study of celestial bodies, including their possible influence on human affairs," borrowed from Anglo-French & Latin; Anglo-French astronomie, borrowed from Latin astronomia, borrowed from Greek astronomía "study of the stars, especially their movements," from astro- astro- + -nomia -nomy

First Known Use

12th century, in the meaning defined above

Phrases Containing astronomy

• radar astronomy
• radio astronomy
• X-ray astronomy

Kids Definition

astronomy

noun

as·​tron·​o·​my ə-ˈsträn-ə-mē 

plural astronomies

: the science of the heavenly bodies and of their sizes, motions, and composition

astronomer

-mər

noun